Carburetor



June 11, 1963 w. w. DEGENHARDT 3,093,698

CARBURETOR Filed March 3, 1961 4 Sheets-Sheet 1 4-, F IG. 3.

' INVENTOR. WILMAR w. DEGENHARDT F IG. 2. BY

AGENT June 1963 w. w. DEGENHARDT 3,093,698

CARBURETOR Filed March 3, 1961 4 Sheets-Sheet 2 F|G.4. F|G.5.

INVENTOR. WILMAR W. DEGENHARDT AGENT June 11, 1953 w. w. DEGENHARDT 3,

CARBURETOR 4 Sheets-Sheet 3 Filed March 5, 1961 FIG.6.

JNVENTOR. WILMAR W. DEGENHARDT AGENT June 1963 w. w. DEGENHARDT 3,093,698

CARBURETOR 4 Sheets-Sheet 4 Filed March 5, 1961 INVENIOR. WILMAR W. DEGENHARDT AGENT United This invention relates to carburetors for internal combustion engines.

The present invention contemplates the provision of a carburetor particularly adapted for use with small internal combustion engines, such as outboard marine engines and other applications. As the horsepower of these engines has become greater there has been an increasing demand for greater fuel economy and better control of engine operation, during the range of engine speeds from idle to full speed.

It is therefore an object of this invention to provide a novel controllable fuel supply system for a carburetor.

It is another object of this invention to provide a novel fuel supply system for a carburetor to accurately proportion the fuel and air mixture of the carburetor to meet engine requirements throughout the range of engine speeds.

A further object of the invention is to provide a carburetor embodying an idle fuel system interconnected with a main fuel system, which is selectively operable responsive to manual operation of a throttle valve.

Another object of the invention is to provide a carburetor adaptable to small engines and which is inexpensive in construction and reliable in operation throughout the speed range of an engine.

The invention embodies other novel features, details of construction and arrangement of parts which are hereinafter set forth in the specification and claim and illustrated in the accompanying drawings, forming part thereof, wherein:

FIG. 1 is a top plan view illustrating a carburetor embodying features of the invention.

FIG. 2 is an elevation showing one side of the carburetor of FIG. 1.

FIG. 3 is an elevation showing the opposite side of the carburetor of FIGS. 1 and 2.

FIGS. 4 and 5 are respectively elevations showing opposite ends of the carburetor of FIGS. 1 through 3.

FIG. 6 is a longitudinal section taken along the line 6-6 of FIG. 1.

FIG. 7 is a transverse section taken along the line 7-7 of FIG. 2.

FIG. 8 is a fragmentary section showing the throttle valve in closed position.

FIG. 9 is a fragmentary section illustrating the metering rod as positioned within the main fuel nozzle to control the flow of fuel therethrough.

Referring now to the drawing for a better understanding of the invention, the carburetor is shown as comprising a body 2 having a horizontal mixture conduit 3 (FIG. 6) provided with an air inlet 4, an outlet 6, and a venturi 7 having a throat 8. A flange 1 is provided on the outlet end of the body 2 for attachment to an inlet manifold 5 of an engine E.

A choke valve shaft 9 is jounaled horizontally in hearing apertures formed in the body 2 to support a choke valve 11 for pivotal movement within the air inlet 4. The choke valve 11 is normally maintained in its full open position, as indicated in FIG. 6, by means of a torsion spring'12 (FIGS. 3 and 5) having one end thereof secured to the shaft 9 and its other end secured to the body 2. The choke valve 11 is adapted to be pivoted to its closed or choke position by manual movement of res atent an arm 13 secured to the other end of the choke shaft 9.

A throttle shaft 14 is journaled vertically in bearing apertures formed in the body 2, as shown in FIG. 6, to support a throttle valve 16 for pivotal movement in the outlet 6, the shaft v14 being engaged against axial movement by means of a plate 17 secured to the body by a screw 18 and having an end thereof engaged in an annular groove 19 formed in the shaft. A manually operable control arm 21 is secured to one end of the throttle shaft 14 to control the proportion and quantity of fuel and air supplied to the engine. The throttle valve 16 is biased toward its closed position by means of a helical torsion spring 22 having one of its ends engaging the body 2 and its other end engaging the control arm 21, as shown in FIG. 6.

The body 2, as illustrated in FIG. 6, is provided with a downwardly projectingtubular stem 23 having its lower end internally threaded at 24 for engagement with the lower externally threaded end 25 of a main fuel nozzle 26. The lower end of the nozzle 26 has an enlarged bolt head 27 for engagement by a tool to enable the assembly of nozzle 26 within stem 23 so that it extends through a fitted portion 28 of body 2 into the venturi section 7 of conduit 3. An O-ring '39- forms a fluid seal between nozzle 26 and body portion 28. The portion of the nozzle between its threaded end 25 and the fitted body portion 28 is reduced in diameter to define a fuel Well 29 with the stem 23. A plurality of ports 31 are formed in the nozzle 26 for the passage of fuel into and out of the lower end of the well 29. An air bleed passage 32 is formed in the body 2 leading from the carburetor inlet 4 to the upper end of the well 29.

The upper end of the main fuel nozzle 26 projects upwardly into the venturi 7 posterior to the throat 8 and is provided with a plurality of fuel ports 33. A fuel metering orifice 34 is formed in the lower end 25 of the main fuel nozzle 26 to receive the lower end 36 of a metering tube 37. The upper end of the metering tube 37 is formed with a rounded head 38. Tube 37 is resiliently supported from head 38 upon a helical compression spring 39 seated at its lower end in a metal cup 40 press-fitted into a bore 41 formed in body 2. The metering tube 37 extends for axial movement through a bearing portion of cup 40 and a bearing portion 4 2 of body 2.

The under portion of the body 2 is formed with a downwardly projecting annular flange 43 having a recess 44 therein to receive the rim 42 of a cup-shaped fuel bowl 46. The bottom '45 of the bowl 46 has an aperture 47 to receive the nozzle structure 26. During the assembly of the carburetor, the nozzle 26 is inserted through bowl aperture 47 and into the well portion 29 of stem 23, with a gasket washer 48 between the bottom 45 of bowl 496 and bolt head 2'7. By screwing the threaded end 25 of the nozzle into the threaded end 24 of stem 23, head 27 first forces the bowl rim against a gasket 49 in the recess 44, and then forces the bowl bottom 45 against the stem 23 with gasket 48' making a fluid seal between head 27 and the bowl 46.

A hollow ring-shaped float 51 is mounted on a pin 5-2 (FIG. 7) for pivotal movement within the fuel bowl to actuate a needle valve 53 to control the flow of fuel through an inlet 54 and valve port 56 into the bowl. The float and valve are adapted to coact to maintain a substantially constant fuel level within the bowl. An air vent leads through the body 2 to the bowl. Fuel is supplied from a tank T (FIG. 1) through a conduit 57 and a fuel pump P to the fuel inlet 54. Fuel passes from the bowl 46 through ports 55 of stem 23 into a chamber 66 in the nozzle end 25 below the orifice 34. Fuel flows through metering orifice 34 and orifices 31 to a level in well 29 and nozzle 26 equal to that maintained by float 51 in bowl 46.

In accordance with the invention, the idle fuel system of the carburetor is designed as an interconnected system with the primary fuel system through nozzle 26. The metering tube 37 is formed with a hollow central channel 59 and with closed ends at 36 and 38. The hollow channel 59 extends from a restricted aperture 62 at the lower end of tube 37 which is adapted to be positioned below the fuel level within bowl 26 at all times. At the upper end of the tube 37, aperture 65 connects the inner channel 59 with the chamber 41 in the carburetor body 2. In an intermediate portion of tube 37, four apertures 58 are formed through the tube wall connecting the inner channel 59 thereof with the air flow through the venturi section 7. As shown specifically in FIG. 7, the body chamber 41 is connected by a passage 61 to a bore 70 and a second body cavity 72. An idle port 63 leads from the mixing conduit 3 anterior to the edge of the throttle 16, when it is in its closed position into cavity 72 to provide air to mix with fuel from passage 61. Apertures 64 are provided in the throttle valve 16, as shown in FIG. 6, for .the passage of additional idle air through the throttle, when it is in its closed position. An idle adjustment screw 66 is threaded into bore 70 to control the amount of idle fuel and air mixture passing from cavity 72 through an idle feed aperture 71, which connects bore 70 with conduit 3 and opens into mixture conduit 3 posterior to the throttle 16, in its closed position.

A cam 67 having an inclined surface 68 is integral with the control arm 21 for slidable engagement with head 38 of the metering tube 37. Rotational movement of the control arm 21 and cam 67 will move the metering tube 37 axially to vary the quantity of fuel passing through the orifice 34. The lower end of the metering tube 37 may be provided with one or more sections of different diameters, as shown in FIG. 9, or may be formed with a long tapering surface, whereby the flow area through the orifice 34 can be varied responsive to axial movement of the metering rod. As for example, the tip 36 of tube 37 provides a high speed flow of fuel through orifice 34, while larger section 39, when inserted into orifice 34, provides an economy flow of fuel through nozzle 26.

In the operation of the carburetor thus shown and described, fuel is drawn from the tank T and through the conduit 57 to the intake 54 by the pump P, and thence through the valve port 56 into the fuel bowl 46 under control of the float actuated needle valve 53 to maintain the fuel at a predetermined level within the bowl and fuel well 29.

During operation of the engine E, the control arm 21 is manually pivoted to move the throttle valve 16 to a partly open position. The air flow through the mixture conduit 3 forms a sub-atmospheric pressure area in venturi 7 to cause fuel to be drawn upwardly through the main nozzle 26 and out through the ports 33 into the mixing conduit 3.

Further gradual pivotal movement of the control arm 21 moves the throttle valve 16 toward its full open position and permits the spring 39 to raise the metering tube 37 as the latter passes along the inclined surface 68 on the cam 67 to thereby increase the flow area and the volume of fuel flowing through the orifice 34 for passage upwardly and out through the upper end of the main nozzle 26 into the center of the mixture conduit 3.

When the throttle valve 16 is opened quickly to provide rapid acceleration of the engine, additional fuel and air is drawn from the well 29 through the openings 31 into the main nozzle 26 for discharge therefrom into the mixing conduit 3.

By providing a manually operable mechanical means for simultaneously operating the throttle valve 16 and metering tube 37, the quantity and proportion of fuel and air may be accurately controlled to effect a material saving in fuel and an improvement in engine performance during idling, part throttle, acceleration, and full throttle.

l In the operation of a boat equipped with two or horsepower outboard engines, it will be appreciated that such a saving in fuel is of major importance, as it decreases the cost of operation and permits an increase in the range a boat may travel when supplied with a predetermined quantity of fuel.

During idle operation of the engine E, the throttle valve 16 is in its closed position and fuel is supplied to the mixture conduit through the idle system. Under such conditions there is a flow of sufiicient air for idling through apertures 64 of the throttle plate '16. In the carburetor during idle, the region of lowest air pressure is immediately posterior to the closed throttle valve 16 and in the carburetor outlet 6. This point of 10W pressure is one which is reflected back through the idle feed aperture 71, passages 61 and 59 to the surface of the fuel in the metering tube channel 59. The fuel, under atmospheric pressure, in bowl 46 is forced upwardly through the hollow metering tube 37 into passage 61. Simultaneously, air will bleed through the apertures 58 exposed to the air flow in the conduit 3 so that there is a flow of a mixture of fuel and air through the upper end of the metering tube 37 and through passage 61 into the body chamber 72.

This mixture of air and fuel provides the idling operation of engine E. Adjustment of the idle screw 66 will provide the correct amount of fuel and air mixture through the idle feed aperture 7.1. The size of apertures 58 in tube 37 determine the amount of air to be mixed with the fuel for idling purposes. These apertures 58 are non-directional and are not affected by their position in the conduit 3.

As the throttle opens from closed position with the engine running, the operation of the carburetor is transferred from the idle system to the main fuel supply system through nozzle 26. As the throttle valve 16 passes the idle feed aperture 71, the vacuum or low pressure in bore is broken and fuel ceases to flow through aperture 71. To aid, however, in the transfer from the idle to the main fuel feeding system, the idle port 63 will pass a mixture of fuel and air from chamber 72, due to the low pressure conditions existing at port 63 as the rim of the throttle valve 16 moves over port 63. By the time, however, that the throttle passes port 63, the nozzle 26 has become fully operative to take over the running of the engine. The length of the slot 63 determines when the nozzle 26 takes over the feeding of fuel to the engine. The idle port 63 can be of a length determined by the operating characteristics of the engine and by the richness of the idle mixture desired. Port 63 may be a slot extending parallel to the axis of mixture conduit 3 with a length from 0.015" to 0.030", for example, in the type of carburetor described. The length of the slot is varied in a direction away from the closed position of throttle valve 16.

In a carburetor of the type described above and suc cessfully operated with a two cycle 60 HF. engine, the venturi 8 of the carburetor was one that has a 1 diameter. The jet size 34 of the carburetor was 0.098. The high speed diameter rod section 36 was of 0.058, while the economy speed section 39 of tube 37 was of 0.079 diameter.

Certain structures have been described herein which will fulfill all the objects of the present invention, but it is contemplated that other modifications will be obvious to those skilled in the art which come within the scope of the invention as defined by the appended claim.

I claim:

A carburetor for an internal combustion engine and comprising a bodly including a mixture conduit adapted to be horizontally disposed and having an inlet, an outlet and a venturi surface therebetween, a throttle valve in said outlet, a throttle shaft journaled in said body and secured to said throttle valve, a fuel bowl mounted on said carburetor body, means forming a tubular fuel passage extending from said body and terminating at one end in said bowl, a main fuel nozzle formed at the other end of said fuel passage means and projecting through said venturi surface into said mixture conduit, means forming in said one terminating end of said fuel passage a metering orifice, a movable metering tube extending through said mixture conduit and said nozzle and having a tapered end extending through said orifice to vary the flow area th-erethrough, an opening from said fuel bowl into said fuel pass-age means for the diow of fuel from said bowl upwardly through said nozzle, an idle fuel system including a fuel passage extending axially through said metering tube into a portion of said carburetor body above said mixture conduit, said metering tube having a port above said orifice connecting said axial fuel passage with said fuel passage means, said carburetor body portion having an idle fuel passage connected to said axial fuel passage and having an opening into said mixture conduit posterior to said throttle valve, said metering tube having a second port connecting its axial fuel passage with said mixture conduit anterior to said throttle for bleeding air into said axial fuel passage, and mechanical means to actuate said throttle valve and metering tube simultaneously to variably proportion the fuel air mixture supplied to satisfy engine requirements at different speeds, said mechanical means comprising a spring biasing said metering tube in one direction, a control arm secured to said thr-otle shaft, and a cam on said control arm engaging the other end of said metering tube for moving said metering tube against said biasing spring.

References Cited in the file of this patent UNITED STATES PATENTS 1,872,559 Bioknell Aug. 11, 1932 2,024,419 Ball et al Dec. 17, 1935 2,402,208 Read June 18, 1946 2,656,166 Foster Oct. 20, 1953 2,656,167 Phillips Oct. 20, 1953 2,674,443 Bracke Apr. 6, 1954 2,827,272 Phillips Mar. 18, 1958 2,986,381 Jones May 30, 1961 

